1. Field of the Invention
The present invention relates to a sheet feeding device which feeds a sheet and an image forming apparatus.
2. Description of the Related Art
In a conventional sheet storing portion which is arranged in a sheet feeding device and which stores sheets, a sheet tray which supports a sheet stack and a side regulating plate to regulate and position the sheet stack supported on the sheet tray are arranged. The side regulating plate is arranged movable depending on a size of a sheet to be supported. A notched portion is formed in the side regulating plate to make it possible to move the side regulating plate.
However, when the side regulating plate is long in a sheet feeding direction, skew feeding of a sheet is regulated and to make it possible to stably feed the sheet. However, when the side regulating plate is long, the notched portion formed in the sheet tray increases in size. For this reason, the sheet is hanged down by its own weight from the notched portion of the sheet tray. As a result defective feeding that a sheet cannot be fed or is skew-fed is caused. Alternatively the sheet is fed while being bent to cause defective recording.
As countermeasures against this drawback, for example, a sheet feeding device having configurations shown in FIGS. 8 and 9 is proposed. These diagrams are plan views showing a main part of a sheet storing portion. In the sheet storing portion, a sheet tray 21, a side regulating plate 25, and an auxiliary plate 30 are arranged. The sheet tray 21 is vertically movably arranged in the sheet storing portion. The sheet tray 21 can support and lift up a recording sheet P. The side regulating plate 25 can be moved in a sheet width direction (perpendicular to a sheet feeding direction) depending on a size of a recording sheet supported by the sheet tray 21. The side regulating plate 25 regulates side edges of the recording to position the recording sheet.
In the sheet tray 21, a notched portion 27 is formed to avoid interference of the side regulating plate 25 in a moving state. The auxiliary plate 30 is swingably arranged on the sheet tray 21 by using a pin 31 as a rotating shaft. The auxiliary plate 30 partially covers the notched portion 27 (part corresponding to a rear-end portion of the recording sheet) to support the recording sheet P together with the sheet tray 21.
As shown in FIG. 8, the auxiliary plate 30 supports a recording sheet P having a large size placed on the sheet tray 21 depending on the recording sheet P not to hang down the recording sheet P in the notched portion 27. As shown in FIG. 9, when a recording sheet P having a small size is stored, the auxiliary plate 30 is swingably retreated depending on movement of the side regulating plate 25. As a technique which prevents a sheet from being hanged down by using such an auxiliary plate, a technique is disclosed in Japanese Patent Application Laid-open No. 2001-097564. However, in a conventional technique, in a large-size sheet storing portion to store recording sheets having large sizes, a side regulating plate is long in a sheet feeding direction, a notched portion of a sheet tray is large in a recording sheet feeding direction. In the large-size sheet storing portion copes with sheets having small sizes (for example, B5, A4, post card, or the like), since a moving range of the side regulating plate in a recording width direction increases, a notched portion of the sheet tray increases in a width direction of a recording sheet.
When the notched portion of the sheet tray is large, the above auxiliary plate which covers only a rear-end portion of a recording sheet is so insufficient that the recording sheet cannot be prevented from being hanged down.
Therefore, in the large-size sheet storing portion, the side regulating plate may be shortened or separately arranged to reduce a notched portion formed in a sheet tray in size so as to assure a holding surface of a recording sheet.
However, in the configuration, since a recording sheet regulating surface of the side regulating plate is shortened, the effect prevents the recording sheet from being skew-fed is considerably deteriorated.